Lateral line pathways and connections are being studied by experimental neuroanatomical methods in the clearnose skate, Raja eglanteria. Primary neurons carrying information from electroreceptors (ampullae) and mechanoreceptors (neuromasts) project differentially to medullary centers and this separation is preserved at midbrain levels where second-order neurons terminate within a large lateral mesencephalic nucleus situated beneath the optic tectum. Emphasis is being given to the efferent projections of this midbrain center in order to determine whether lateral line neurons reach the telencephalon. Silver degeneration (Fink-Heimer), radioautographic (tritiated proline/leucine), and horseradish peroxidase methods are being used to study the course and termination of lateral line neurons beyond midbrain levels.